High-intensity pulsing circuits



Patented Nov. 8, 1949 UNITED STATES PATENT OFFICE HIGH-INTENSITY PULSING CIRCUITS Donald E. Watts, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 22, 1941, Serial No. 407,951

this character comprising a transmitter arrangement capable of relatively high peak power output.

In accordance with the present invention this object is attained, in a system including for example an amplifier of a given maximum continuous power output capability and having an anode circuit connected to a source of relatively extremely high voltage and a control electrode circuit energized from a keyed oscillator, by the provision of a resistor-capacitor circuit means associated with the anode circuit of the amplifier which permits the peak power output in a load or utilization circuit of the system to be relatively high during a series of pulses produced by normal keying of the amplifier but which limits the amplifier to the above-mentioned maximum continuous power output if the keying device is held continuously closed longer than a predetermined time interval.

The novel features which are considered to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing wherein Fig. 1 is a diagrammatic representation of a pulsing system embodying my invention, and Fig. 2 is an equivalent circuit diagram illustrating the invention.

In Fig. 1, the numeral I indicates generally an amplifier or like device which may include two electron discharge devices 2 and 3 each having a cathode 4, an anode 5, and a control electrode 6. The anodes 5 are connected respectively to opposite ends of a winding 1, the cathodes 4 are connected together and preferably grounded. and the control electrodes 6 are connected respectively through grid resistors 8 and condensers 9 to a source of preferably radio frequency oscillations indicated generally by the rectangle H). Source It) may be a balanced oscillator of a usual type or such as described in the application of Donald E. Watts and Paul C. Gardiner, Serial No. 311,532, filed December 29, 1939 and assigned to the same assignee as the present invention (now Patent 2,400,796 granted May 21, 1946), or any other suitable source such as an intermediate amplifier. The oscillator In or intermediate amplifier is adapted to be keyed by a keying device of any e 2 suitable form represented generally by the rectangle l.

The control electrodes 6 are connected through choke coils l2 and a resistor [3 to a source 14 of biasing potential which is of such value that the devices 2 and 3 are in the non-conducting or cut-oil condition when radio frequency potentials are not being impressed on the control electrodes 6 from the oscillator l0. Capacitors l5 in series are connected across the winding 1 and the center connection of these capacitors is connected to ground. The anode-cathode circuit IQ of devices 2 and 3 includes a source of relatively high unidirectional potential (not shown) connected through a choke coil ll across the middle point of output winding 1 and cathodes 4. The choke ll is bypassed to ground by a condenser H3.

The circuit connections of circuit l6 include a condenser 19 in series with the unidirectional voltage source and a resistor 28 in shunt with the latter condenser. This resistor-capacitor shunt combination constituted by condenser l9 and resistor 2B is so arranged that its time constant is preferably longer than the pulse duration.

The output coupling winding 2| of the circuit, including output winding 1 and condensers I5, is connected to a load or utilization circuit (not shown) of any desired character. Neutralizing condensers 22 and 23 are preferably provided respectively between the anode of each one of the devices 2 and 3 and the control electrode of the other to prevent undesired oscillations.

In operation of the above described system, assuming initially that anode potential from the source of unidirectional potential is being supplied to the anode-cathode circuit I8 of devices 2 and 3 and that the negative biasing potential sufficient to render devices 2 and 3 non-conducting is being supplied from source M to the control electrodes 6, 6, then current flows in output circuit 56 and in the load circuit associated therewith when the oscillator ID is operated by keying device II to impress pulses of radio frequency oscillations alternately upon the control electrodes of devices 2 and 3.

In accordance with my invention, the potential across the unidirectional potential source is of such high value that the pulses produced in normal keying of the system are of relatively very high peak value, and of a value preferably substantially higher than it is usually desirable to permit the devices 2 and 3 to transmit during continuous operation or key-closed condition of the system because of the danger, under these conditions, of damage to the devices 2 and 3 from overloading. These extremely high power peak pulses may be produced at any desired speed, for example, at speeds of approximately 40 to 400 cycles per second. To protect the devices 2 and 3 from the above mentioned overloading in case the system is left in continuous operation or key-closedcondition; the shunt combination comprising-condenser Is and resistor 20 isso arranged that its time constant is preferably substantially longer than the time periods of the pulses. The manner of operation of the shuntgcombination l9 and 20 in performing this protective'function will be explained hereinafter.

In the use of the system t'o roduce? the normal is high power peak pulses, the series of short pulses of unidirectional current inncircuitii areconducted through the condenser l9 which in the normal condition of operation offers a iew or negligible impedance to;x-the current flow. There- -fore during this'znormal condition :of operation, substantially the full potential of the source-is impressed across theranodesi-and' cathodes of the "devices 2 and 3thereby'producing the'relatively very high pulse peak :current values 'above men- --.tioned,"*withoutshowevergsubjectingtthe'.iievio'es to the danger of damage from'overloading.

Assuming, howeventhat the system is left in zcontinuous ,operati-o'n :ror xkey-"close'd 'rcondition, thensu bstantially continuous current flows in the scirc-uit .-|=6 insteadrof"atheviinidirectional series of rapidly recurring short pulses 'which occur under normal ,or keying r conditions. This continuous 1 current charges the condenser I9 which is shunted by the :resistor 20. Discharge current from the condenser I9:fiowing:iincshunt:resistor 2D'produces a potential drop which is, however, opposite in sign to the potential of the unidirecstional gpoten tial x source. Therefore, iunder Lthis described condition of continuous or key-closed operation-ofthe system, after ashort time interval, e. vg., the timerfor the condenser I am fully ch arge,: thepotential impressedaa'crosszthe'zdevices 2 and 3.is not the. full potential of the unidirectional potential-sou-rce but' is this source potential the *drop through the rresistor 'lll, the lresultant lower potential being preferably the po- -tential corresponding to the: given: m'aximunrccn tinuous power output capability of the discharge devices! and 3.

In the use "of the; above-described system I the series of-short high powerpulsesof radio-frequency oscillationsproduced-in the dischargedevices 2 and 3 upon keying "of the oscillator I0 maybe supplied through the coupling coil 2| to any desired load or utilization circuit (not :shown). 'In producing the series of pulses, oscili lationsiofradiofrequency are preferably kept out of thesou-rce o fmnidirectio'n'al potential-bya-ny suitable filtering 'm'eans s'uch'as provided, for example, by condenser I 8 and choke coil IT.

'For a mathematical consideration of the'circuit including the resistorshunt combination constituted bycondenser l9'and. resistor 20 the simple equivalent circuit shown in .Fig. 2 applies.

.In Fig. 2,.E represents thepotential'of theunidirectional potential source of Fig. "1, E'erepresents. the potential.acrossthecondenser1-9, trepresents the total current in circuit I6, is and in represent thecur-rent in condenser 19 and resistor Z-O respectively, C representsthe capacitance ofcondenser: l9,--R the resistance-of the resistor '20, R1, the'load resistance, and t the time interval'fromthe instant thatithe switch is. closed (-or i=0) to the instant that the switch is opened.

Under these conditions,

RR C

At'the instant switch S is closed, the current through 'R' islizerdand the current through E It During the'timeinterval following the closing of :the switch, the current it decreases and the current in increases until period of time the RI drop in resistor R will prevent accidental'damage to the tubes which might occur because of high current and plate dissipation.

During pulse keying, the RC circuit if of suitable values will not allow a steady state condition to be'reached. Thus, highpea'k power output is obtained.

When the.pulse is removed by opening the switch, -the 'cap'a'citorC discharges into resistor R in the opposite direction from that of the current by which it wascharged. It is assumed that the period during which the pulse is off will be of 'suificient magnitude to allow the capacitor to be substantially discharged, thereby allowing thepulse to start again at nearly the same level of power. each time, Such magnitude of the time period is not essential, but it results in a higher level of peak power.

Fora mathematical considerationof theRC' circuitfor the period'from the instant that the switch is first opened to the instant it is again closed, the simple equivalent circuit of Figure .2 again applies.

In this latter case t represents the time from the beginning of closing switch S to the instant when switch S is again closed, t-t1 the time from the instant that switch S is opened to the instant when switch S is again closed, and, t1 the time measured from the instant switchS is firstclosed to the instant switch S is opened.

arrangement but that various other pulse pro- "'ducingdevices and arrangements may be employed in connection with the protection means comprising the resistor-capacitor means.

A pulse generating system as described herein is particularly applicable to the supplying of pinging circuits, for underwater signalling for example. The system is, however, applicable to a large variety of other uses, and in particular to any application requiring high maximum peak pulse power from a transmitting apparatus meeting especially low minimum weight and space requirements.

My invention has been described herein in a particular embodiment for purposes of illustration. It will be understood, however, that the invention is susceptible of various further changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high intensity pulsing circuit comprising, in combination, an electron discharge device having input and anode circuits, means for recurrently impressing a signal pulse of predetermined duration upon said input circuit, said device having increased conductivity during said pulse and being capable of safe continuous operation with a predetermined maximum anode potential if si nals are continuously supplied for longer than the duration of said pulse, a source of anode operating potential of substantially higher value than said predetermined potential, and means for impressing the potential of said source upon the anode of said device through a current-limiting impedance network comprising a condenser and a resistor in parallel, said network having a time constant longer than the duration of said signal pulse, and said resistor havin a value sufiicient to limit the anode potential to a value not exceeding said maximum value under steady state conditions of continuously-applied signals.

2. A high-intensity pulsing circuit comprising,

in combination an electron discharge device having grid and anode circuits, keying means for impressing periodic spaced pulses of high frequency signals upon said grid circuit, means for impressing a negative bias potential on said grid circuit sufficient to maintain said device cut off except when signals are impressed, said device being capable of safe continuous operation with a certain maximum anode potential if input signals are impressed for longer than a predetermined pulse duration, a source of anode operating potential of substantially higher value than said maximum potential, and means for impressing the potential of said source upon said anode circuit through an impedance network comprising a condenser shunted by a resistance, said network having a time constant longer than said predetermined pulse duration and said resistance having a value suilicient to limit the anode potential to a value not exceeding said maximum value under steady state conditions of continuously-applied input signals.

DONALD E. WATTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,455,141 Lowell et a1 May 15, 1923 1,938,742 Demarest Dec. 12, 1933 2,037,799 Koch Apr. 21, 1936 2,098,051 Lord Nov. 2, 1937 2,103,362 Hansell Dec. 28, 193? 2,235,667 Blount Mar. 18, 1941 2,299,388 Hansell Oct. 20, 1942 FOREIGN PATENTS Number Country Date 240,510 Great Britain Sept. 29, 1925 299,856 Great Britain Oct. 24, 1929 

